1. Field of the Invention
This invention relates generally to oil and gas drilling equipment, and particularly to tongs or other equipment used on drilling rigs for coupling and decoupling stands of drill pipe. More particularly, this invention relates to a test stand for testing torque applied by tongs to drill stem.
2. Description of Related Art
In oil and gas exploration and production, a drilling rig is positioned over a well bore site for drilling or reworking a well. During rig operations, a derrick sitting atop the drilling rig's platform repeatedly lifts stands, or segments, of pipe, into a vertical position above the well bore, where each stand is successively joined with the one below which already is inserted into the well bore. Once fully made up, the stand is lowered into the hole, whereupon another stand is lifted and coupled thereto. Within the derrick platform floor, a rotary table grasps in its jaws the upper end of the top segment of pipe already in the hole pending joining to it another stand. The derrick thus chains together stands of pipe for insertion into the well bore, either to serve as casing to line the bore hole, drill stem to turn drill bits at the bottom of the hole to increase bore depth, or production well pipe for extracting oil and/or gas from a producing well.
Typical well pipe joints comprise nominally thirty (30 ft.) foot segments of steel tube having an outside diameter of between four and one-half (4.5 in.) to fifteen (15 in.) inches or more, each with male (pin) and female (box) threads on opposite ends thereof. When two pipe segments are being joined, a derrick hand stabs the pin of the upper pipe segment into the box of the lower pipe segment, whereupon other derrick hands spin the upper pipe segment to tighten the threads together. This process seldom if ever tightens the threads enough. To do so, derrick hands commonly employ powered tools known as tongs to spin the upper pipe further until a specific torque is reached. Commonly, a second, lower tong grasps the lower pipe segment to hold it and prevent it from rotating while the upper tong tightens the joint.
Not surprisingly, well pipe, along with the joints between segments thereof, endure significant torque, compression and tension pressures during operation. Poorly mated pipe joints can flex, wobble and break under such pressures. A need exists for means to assure that pipe joints are tightened to specified torques to prevent such mishaps.
Power tongs engage and turn pipe to predetermined torque settings within the machinery itself. Unlike with smaller pipe and manual tongs, a derrick hand must rely upon the power tongs to exert sufficient torque to join the pipe segments together. If a power tong unit cannot produce the required torque and rotate the upper pipe sufficiently, the derrick hand has no means for determining whether or not the make-up was performed properly. A need exists for means for testing torque output of power tongs to assure that they meet standards prior to being used on drilling rigs.